#include <stdio.h>
#include <string.h>

void concatenateString(char *str1, char *str2, char *result)
{
    const char *p1 = str1;
    char *res_ptr = result;

    while(*p1 != '\0')
    {
        *res_ptr = *p1;
        res_ptr++;
        p1++;
    }

    const char *p2 = str2;

    while(*p2 != '\0')
    {
        *res_ptr = *p2;
        res_ptr++;
        p2++;
    }

    *res_ptr = '\0';
}

int main()
{
    const char *str1 = "hello";
    const char *str2 = "World!";
    char result[20];

    concatenateString(str1, str2, result);
    printf("%s", result);

    return 0;
}